For purposes of the present application, the terms "video tape recorders" and "video cassette recorders (VCRs)" are used interchangeably. Moreover, as used herein, the term "broadcast" refers not only to transmission by airwaves, but also to other forms of transmission, such as by cable.
Many presently available VCRs are programmable. That is, such VCRs can be programmed to begin to record TV broadcast material or cable material at a particular time on a particular day by means of a control panel or a remote control device. Moreover, built-in VCR programming functions often allow two or more programs, broadcast on different channels and at different times of the day or week, to be entered into the system. Termination times for respective recording operations are similarly programmable.
VCR programming functions such as those described above are time-dependent. In order to specify the initiation or termination of programming functions, the time of day as well as the day in the week must be specified. Unfortunately, the time clocks in present VCRs can be interrupted and set to the incorrect time by a variety of random factors such as by a short power interruption. Furthermore, the random access memories used to store other information in such systems are generally volatile memories, requiring periodic refreshing to maintain data. Thus, if power levels are degraded or interrupted for even a short period of time, the data that drives the timing circuitry is either corrupted or lost, resulting in inaccurate or indeterminable time values displayed on the VCR clock. These situations can result in recording unintended rather than desired broadcast material.
Over a period of days or weeks, the probability of power fluctuations or interruptions which will cause the system clock to lose synchronization with the correct time increases. Ensuring integrity and maintaining reliability in programmed video tape activities, regardless of power outage situations, is therefore a problem.
A related problem concerns setting and resetting the VCR clock. Resetting operations can be mandated by certain predictable events such as the onset of daylight savings time and time zone changes.
One attempted solution to the foregoing problem has been to supply a backup battery which is used in case normal power is interrupted. This solution is not entirely satisfactory for various reasons. For example, battery replacement is costly, it is difficult to know when a battery has discharged, it is inconvenient to replace a battery, and a battery uses valuable space.
Another attempted solution to the foregoing problem of unreliable power supplies has been to provide a non-volatile memory device for storing use programmed system timing information in the event of a power outage. This solution, however, requires relatively expensive and complex circuitry and generally still requires a battery backup to keep the clock operating without external power.
The present invention also addresses the need to descramble programs transmitted via cable or satellite. Encoding, scrambling or encrypting of specific material, generally transmitted by means of cable, is becoming increasingly more common. Decoding or descrambling operations are generally not automatic. They normally require human intervention at the cable distributor to receive information from one or more subscribers and to take appropriate action to decode the signal.
U.S. Pat. No. 4,771,456 issued to Martin et al discloses one of many descrambling techniques that can be used. In order to make such descrambling operations highly effective, it would be desirable periodically to change code words used to descramble the programs. Furthermore, it would be highly desirable to be able to program specific video tape recorders remotely by using a code word to enable the specific receiver to receive particular, preselected program material. The aforementioned facility would greatly enhance the billing options which could be utilized by cable operators.
Another problem with present video recorders is the difficulty of programming them in a completely flexible manner. Present video cassette recorders must be programmed by use of a relatively lengthy set of commands entered at the VCR control panel or remote control device at the location of, or a short distance from, the VCR. Entering a long set of commands manually is a time consuming, difficult operation which is prone to errors.
In fact, significant problems are encountered by users of presently existing VCRs. From setting the VCR clock to programming a VCR for unattended operation, a considerable degree of skill and care is required. It is necessary to select the station, the day of the week, the time (including a.m. or p.m.), and the length of the program for each program to be recorded. Some VCR owners are unable to master the complexities of setting the VCR for unattended operation, and simply do not use that feature of the equipment. Almost all users, at one time or another, have recorded undesired material through an incorrect setting of the VCR. U.S. Pat. No. 4,706,121 issued to Young discloses a system for recording TV broadcast material from preprogrammed scheduled information; however, the system shown in that reference adds only a limited amount of function to a VCR.
Another limitation of present video recorders is that they do not provide any mechanism for storing messages. Furthermore, people who use paging systems generally must turn from their TV receiver to an entirely separate system to receive messages that are paged to them.